A torque wrench is typically used to exert a given torque on connecting elements, such as screws or nuts. For this purpose, torque wrenches comprise a wrench lever with a grip and a wrench head, referred to as head portion hereafter. Often, a coupling in the form of a square fitting is provided at the wrench head to receive a insert tool. Different insert tools for rotating screws or nuts can be fixed on the square fitting. A force exerted on the grip by a user in the operating direction is transferred from the wrench lever to the wrench head and generates a torque on a screw or nut through the insert tool. In order to measure the exerted torque the torque wrench is provided with a measuring device. With further devices the measured torque is continuously displayed or the reaching of a given torque is indicated.
The measuring device of a torque wrench is normally subjected to common wear and tear symptoms. The torque wrench must be calibrated from time to time with an operating device to check if a torque measured with the measuring device is the same as an exerted torque. A carrier with a transducer and a grip holder is provided in the operating device. The head portion of the torque wrench is tightly coupled to the transducer, for example with the square fitting. The grip of the torque wrench is fixed by the grip holder.
A torque is exerted on the head portion of the torque wrench by a deflecting mechanism. This torque is measured by the transducer and displayed in a display provided at the operating device, for example at the transducer. The torque displayed by the torque wrench or a torque set for the torque wrench for a release can be tested by comparison with the torque displayed on the display.
With known operating devices for testing torque wrenches different deflecting mechanisms for the generation of a torque are used. In principal two ways are possible for the generation of a torque at the head portion of a torque wrench. Either the transducer is rotatably fixed to the carrier and the grip holder is immoveable fixed to the carrier or, in the other way, the transducer is immoveable fixed to the carrier and the grip holder is moveably mounted on the carrier.
The operating devices according to the prior art having grip holder which is moveable with respect to the carrier comprise a linear actuator with a spindle and a crank. By rotating the spindle by means of the crank the grip holder and thereby also the grip of the torque wrench are deflected perpendicular to the carrier. Thereby a torque is exerted on the head portion which is fixed to the transducer. The torque wrench is tilted about an axis of the transducer. The grip is moved in a circle rather than the linear movement of the grip holder and it must, therefore, be moveably held in the grip holder.
Such an assembly has the disadvantage that the origin of force changes during the testing procedure. The more the torque wrench is tilted the more the origin of force moves to the outer end of the grip. Thereby the lever length is changed during the testing procedure. This circumstance causes measuring errors when a torque wrench is tested.
Furthermore the grip holder must be shifted on the carrier together with the linear actuator in order to adapt the operating device for torque wrenches having a different size. Accordingly, the linear actuator must be very large for very large torque wrenches. Thereby the set-up of such an operating device is complicated and difficult to handle.
The disadvantage of different origins of force is avoided with the known operating devices for testing a torque wrench where the transducer is rotatable with respect to the carrier. The torque wrench is locked with the head portion at the transducer and the grip is fixed by the grip holder. In one modification a torque is exerted on the transducer and the head portion through a crank and a gearing. It is disadvantageous with such operating devices that there is a gearing having many complex individual components. The gearing causes the operating device to be large, especially in height.
In a further known embodiment of the operating device the transducer is mounted on a basis having a spindle with a crank fixed thereon as a linear actuator. The carrier is rotatably fixed to the transducer and can be tilted with the crank and the spindle. In such a way a gearing is avoided but the operating device is also assembled with many individual components due to the additional basis. Furthermore the operating device requires much work space due to the basis and the carrier which is tilted as a whole.